1. Field of the Invention
The present invention relates generally to a wireless sensor network, and more particularly to a method of allocating multi-channels in a wireless sensor network using the multi-channels.
2. Description of the Related Art
Substantial research has been performed on multi-channel Medium Access Control (MAC) protocols for improving the performance of an ad-hoc network for use in a computer, which is a type of wireless network. However, there is a problem with such ad-hoc network protocols in that it is difficult to directly apply them to an ad-hoc network due to the characteristics of a sensor network, such as insufficient resources, computing power, and cost. Accordingly, there has been substantial research on several multi-channel MAC protocols suitable to a sensor network.
Among these multi-channel MAC protocols is the core technology of allocating multi-channels to respective nodes in a network, which is important to control the performance of the multi-channel MAC protocol. Conventional channel allocation methods by network environments will now be described.
In a wireless sensor network environment such as a Multi-Frequency MAC for wireless Sensor Network (MFSN) environment, each node in a network is allocated with an exclusive frequency or channel for receiving data through exchange of a channel allocation message with a neighboring node located within a 2-hop distance. In the MFSN environment, a fixed channel allocation method is used, and thus the number of available channels is fixedly determined in accordance with the corresponding network environment. This method is useful when the number of nodes within a 2-hop distance is smaller than the number of available nodes.
When the number of nodes within a 2-hop distance is larger than the number of available nodes, a random channel allocation method is used. In this case, channel collision occurs and deteriorates the performance of the network. That is, normal operation is performed when the number of available channels is larger than the number of nodes within a 2-hop distance. However, an overlapping channel is allocated to adjacent nodes causing channel collision when the number of available channels is smaller than the number of nodes within a 2-hop distance. In the network environment having a high node density, this phenomenon occurs more severely and causes substantial performance deterioration.
In a wireless sensor network environment such as a Multi-Channel MAC Protocol for wireless Sensor Network (MCSN), the entire network is divided into plural clusters, and a cluster member node requests a channel for data transmission and a time slot from a cluster head using an on-demand method when data to be transmitted is generated. The cluster head schedules a channel and use time based on such a request message, and allocates the channel and the use time to the cluster member that has requested the channel. However, this method has limitations in that it is useful only in a specified network environment adopting the clustering. That is, a separate clustering mechanism is required, and considerable time and energy may be consumed to perform the clustering mechanism, thus causing performance deterioration of the entire network. Also, since this method is useful only in the specified network using the clustering, the flexibility of the algorithm is decreased accordingly.